Concrete floor



N. F.l AMBURSE'N'.

CONCRETE FLOOR.

APPLICATION FILED APR. 27,l I9Ia.

1,334,729. Patented Mar. 23, 1920.

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. UNITED sTA'rEs PATENT ormoni.

NILS FREDERICK AMBURSEN, OF NEWTON, MASSACHUSETTS, ASSIGNOR TO THE UNLFORM COMPANY, 0F BOSTON, MASSACHUSETTS, A CORPORATION OF MASSACHU-SETTS.

CONCRETE `FLOOR.

Specification of Letters Patent.

Patented Mar. 23, "1920.

Application filed April 27, 1918.` Serial No. 231,175.

To all whom it may concern:

Be it known that I, NILs FREDERICK AM- nURsnN, a citizen of the UnitedStates, and a resident of Newton, in the county of MiddleseX and Stateof Massachusetts, havev invented a new and useful Improvement inConcrete Floors, of which the following is a specification.

My invention relates to monolithic concrete floors or roofs molded inposition by means of suitable forms such for example as those describedin my application, Serial No. 229,168, iiled April 17, 1918, on whichLetters Patent No. 1,292,986 were issued February 1, 1919.

The primary object of my invention js to provide a monolithic flat-slabconcrete floor or roof which for a given load shall require the minimumamount of material.

An illustrative` embodiment of my invention is shown in the accompanyingdrawings in which Figure 1 is an inverted plan view of a portion of afloor or roof embodying my invention, such portion being located betweenthe supporting columns and the drop panels carried thereby, mif thelatter are employed; Fig. 2 is a transverse section taken on the line2-2 of Fig. l; Figs. 3 and 4. are diagrams hereinafter referred to inexplaining the theory upon which my invention is based; and Fig. 5 is adiagrammatic plan View of the usual flat-slab floor of the prior art ofwhich Fig. 3 is a diagrammatic section.

My improved monolithic flat-slab floor, in the particular exampleselected for more fully disclosing the principle of my invention,comprises the usual flat-slab floor 1 having on its lower surface aplurality of shallow, laterally-spaced ribs 2, the width of each ofwhichis at least twice its depth, there being a number of such ribs, allrunning in the same direction between a pair of the usual supportingcolumns (not shown) and the said ribs extending longitudinally of thefloor when `the latter is oblong. Embedded within each rib arereinforcing members 3 which may be metallic rods, said members beingsupported in the mold before the concrete is poured by the spacingmember 4 which of course remains in the molded structure after the formshave been taken down. Another system of reinforcing members 5 isembedded in the floor proper and extends transversely of the same.

The two systems of reinforcing members vare angularly related andpreferably are arranged at right angles to each other. The members 3 ofthe longitudinal reinforcing system are located partly or wholly belowthe plane of the lower surface of the floor proper and as shown in Fig.2 they are preferably wholly below said plane. In

Fig. 5 which represents in diagram a bay or panel of the usual {iat-slabfloor of the prior art, the floor slab 1 is supported directly on thecolumns 6 without the intervention of beams or girders and 7 indicatesthe usual drop panels now generally employed for reducing the negativebending moments and increasing the shearing resistance over the tops ofthe columns. i Such a floor, as is well understood by those skilled inthis art, is a beamless and girderless monolithic concrete floorconsisting of concrete slabs supported directly on columns. 'The presentinvention is an improvement on such lat-slab floor of the prior art.

The area of the steel constituting the reinforcing system of a floorvaries inversely as the distancesbetween the centers of the respectivemembers thereofand the top of the floor, or, more strictly speaking, theneutral axis of the floor, such neutral axis being about one-third ofthe depth of the slab below the surface of the floor. It will thereforebe apparent that a saving in the amount of material required for a givenfloor may be eEected by increasing said distances, provided however thatthe amount of concrete is not thereby augmented so greatly as to offsetsuch saving.

In Fig. 3 I have sho-wn the usual flat slab Hoor in which one system ofreinforcing members rests directly upon the other, d, d representing thedistances between the centers of the respective reinforcing members andthe top of the floor. If these distances are increased by making thefloor thicker, the gain secured by reducing the area of the steel ismore than offset by the extra amount of concrete required. owever asshown by Fig. 1, I am enabled to materially increase these distances bymeans of the ribs 2 which require in their construction only acomparatively small additional amount of concrete.

As indicated by the cross-sectioned portion of Fig. 4:, the thickness ofthe ribbed licor in the case of a square oor may be reduced for a givenload, the material thereby saved being much greaterthan that requiredfor constructing ribs. reinforcing members is embedded in the ribs andas the distance D from the center thereof to the top of the ioor isgreater than the distance d of Fig. 3, the area of the steelconstituting this system may be reduced. The other system may be loweredso that the distance D from the center thereof to the top of the flooris equal to d of Fig. 3 and the area of the steel constituting the samealso reduced.

I have found that for a given load, a

i lioor constructed in accordance with my invention requires lessmaterial than a flat slab floor of the type shown in Fig. 8. In

the case of an oblong floorithe saving of material is quite marked forthe following reasonr'The thickness D of the floor is necessarilydesigned with reference to the longer span. Had the iloor been designedwith reference to the shorter span, its thickness would have been D",but the longer span and the greater thickness necessarily governs. By myinvention I am enabled to limit the dimension D to the ribs only whileretaining for the'slab the dimension D which is the correct thicknessfor the shorter span. I have therefore saved abody of concreteequivalent to the thickness Dlv between the ribs, and, inasmuch as thedead weight is thereby reduced, it necessarily follows that the area ofsteel will be correspondingly diminished. Y

Another advantage secured by the construction above described is thatthe reinforcing 'rods arev not in Contact and therefore may be entirelysurrounded by concrete, thereby eliminating a defect inherent in flat,slab floors of the prior art in which the 'bond between the con-creteand a pair of i crossed rods is faulty.

bers, one system lying` above the plane of the lower surface of the Hoorand being embedded in said slabs and the other system One set of lyingbelow said plane and being embedded in said ribs.

2. An oblong beamless and girderless monolithic concrete floorconsisting of concrete slabs supported directly on columns, said slabshaving a plurality of shallow laterally-spaced longitudinally-extendingribs on the lower surface thereof, there being a number of such ribs,all rimning in the same direction, between a pair of supporting columnsbut not intersecting the latter nor terminating therein, the thicknessof the ribbed portion of the floor depending upon the length of thelonger span of said ioor and the thickness of the slab portion dependingupon the length of the shorter span thereof and two systems ofangularly-related reinforcing members, one system lying above the planeof the lower surface of the floor and being embedded in said slabs andthe other system lying below said plane and being embedded in said ribs.

8. A beamless and girderless monolithic concrete floor consisting ofconcrete slabs supported directly on columns, said slabs having aplurality of laterally-spaced ribs on the lower surface thereof, thewidth of each rib being at least twice its depth, there being a numberof such ribs, all running in the same direction, between a pair ofsupporting columns but not intersecting the latter no1` terminatingtherein, and two sys- -i tems of angularly related reinforcing members,onesystem lying above the plane of the lower surface of the floor andbeing embedded in said slabs and the other system lying below said planeand being embedded in said ribs.

4. An oblong beamless and girderless monolithic concrete Hoor consistingof concrete slabs supported directly on columns, said slab-s having aplurality of laterallyspaced longitudinally-extending ribs on the lower,surface thereof, the width of each rib being at least twice its depth,there being a number of such ribs, all running in the same directionbetween a pair of supporting columns but not intersecting the latter norterminating therein, the thickness of the ribbed portion of the floordepending upon the length of the longer span of said {ioor and ythethickness of the slab portion depending upon the length of the shorterspan thereof, and two systems of angularly-related reinforcing members,one system lying above the plane of the lower surface of the floor andvbeing embedded in said slabs and the other system' lying below saidplane and beying embedded in said ribs.

In testimony whereof, I have hereunto subscribed my name this 24th dayof April, 1918.

NILS FREDERICK AMBURSEN.

